1. Field of the Invention
This invention relates to an endoscopic operation instrument having an operating portion formed by elastic wires provided with a tendency to expand outwardly.
2. Description of the Prior Art
A basket type forceps, as an endoscopic operation instrument, has an operating portion provided at the distal end of an actuating member slidably inserted in a flexible sheath. This operating portion is formed in such a manner that the proximal ends of elastic wires are connected to the distal end of the actuating member by a rear end tip, that the distal ends of the elastic wires are clamped together by a front end tip, and that bent portions are formed in the intermediate portion of the elastic wires to provide the operating portion with a tendency to expand outwardly. Thus, when the actuating member is pushed and pulled to thrust the operating member out of and into the distal end of the flexible sheath, the operating portion can be opened and closed so as to grasp foreign bodies or remove polyps.
In the operating portion of the above-mentioned conventional endoscopic instrument, the bent portions of the elastic wires are formed at the same position in the axial direction of the actuating member. Therefore, in order to pull the operating portion into the flexible sheath, a plurality of bent portions must be deformed simultaneously, so that the pulling operation is heavy, thereby affecting the handling of the instrument.
Further, when the operating portion has been pulled into the flexible sheath, a plurality of bent portions press against substantially the same position on the inner surface of the flexible sheath, so that the contact resistance therebetween increases. Thus, a large actuating force is also necessary to thrust the operating portion out of the flexible sheath, thereby affecting the handling of the instrument.
The similar problems are observed in the case of a diathermic snare, as another example of endoscopic operation instrument, having an operating portion formed by folding back a single elastic wire.